1. Field of the Invention
The present invention relates to a method of and an apparatus for fabricating an oxide superconducting wire, and more particularly, it relates to a method of and an apparatus for fabricating a wire which comprises an oxide superconducting film formed on the surface of a long base material.
2. Description of the Background Art
As a method of fabricating an oxide superconducting wire, there has been developed a method of charging powder of an oxide superconductive material into a silver pipe and wire-drawing the same, a method of depositing a thick film of an oxide superconductive material on a flexible base material by plasma flame coating, or the like (hereinafter referred to as first prior art).
On the other hand, a laser deposition process has been proposed a method of forming a thin film of an oxide superconductive material, although the same is not yet applied to fabrication of an oxide superconducting wire. In relation to such laser deposition, an excimer laser, a nitrogen laser, the second harmonics of a YAG laser, a CO.sub.2 gas laser or the like is employed to deposit an oxide superconducting film of Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O or Tl-Ba-Ca-Cu-O on a base material of strontium titanate, magnesium oxide or the like, thereby obtaining a high-quality film (hereinafter referred to as second prior art). As to the second prior art, refer to Appl. Phys. Lett. 53, 1557 (1988) by B. Roas et al., for example.
In the first prior art, however, there is no control method of desirably orienting current anisotropy of the oxide superconductive material longitudinally along the wire, and critical current density, which is the most important factor of the wire, has been limited to about 10.sup.4 A/cm.sup.2 at the liquid nitrogen temperature.
In the second prior art, on the other hand, the area of a film which is formable on a single-crystalline base material of strontium titanate, magnesium oxide or the like is limited to about 2.times.2 [cm.sup.2 ]at the most, although the film is of high quality with critical current density of 10.sup.6 A/cm.sup.2 at the liquid nitrogen temperature. Thus, it has been substantially impossible to form the film on a long base material, in order to fabricate a superconducting wire.